Field
The present disclosure generally relates to methods and apparatuses for processing a substrate, and more specifically to methods and apparatuses for controlling photoresist line edge/width roughness.
Description of the Related Art
Integrated circuits have evolved into complex devices that can include billions of components (e.g., transistors, capacitors and resistors) on a single chip. Photolithography may be used to form components on a chip. Generally, the process of photolithography involves several basic stages. First, a photoresist layer is formed on a substrate. The photoresist layer may be formed using a variety of techniques, such as spin-coating. A chemically-amplified photoresist may include a resist resin and a photoacid generator. Upon exposure to electromagnetic radiation during an exposure stage, the photoacid generator alters the solubility of the photoresist, enabling portions of the photoresist to be removed during a development stage. The electromagnetic radiation may have any suitable wavelength, such as a wavelength in the extreme ultraviolet (UV) range. Electromagnetic radiation may be generated using any suitable source, for example, via a 193 nm ArF laser, an electron beam, an ion beam, or another source. Excess solvent may then be removed during a pre-exposure bake stage.
During the exposure stage, a photomask or reticle may be used to selectively expose certain regions of the substrate to electromagnetic radiation. Other exposure methods may include maskless exposure methods. Exposure to electromagnetic radiation may cause the photoacid generator to release acids, creating a latent acid image in the resist resin. After exposure, the substrate may be heated in a post-exposure bake stage. During the post-exposure bake stage, acid released by the photoacid generator reacts with the resist resin, changing the solubility of the resist resin.
After the post-exposure bake, the substrate and, particularly, the photoresist layer may be developed and rinsed. After development and rinsing, the pattern of the mask is transferred to the substrate.
As processor architectures continue to evolve, higher circuit densities and lower leakage currents become more desirable. The demand for higher circuit densities necessitates a reduction in the dimensions of integrated circuit components. Accordingly, the lithography process must precisely transfer smaller and smaller features onto a substrate without causing damage to the substrate. In order to precisely and accurately transfer features onto a substrate, high-resolution lithography techniques may implement light sources that provide electromagnetic radiation having short wavelengths. Decreasing the wavelength of electromagnetic radiation used during lithography enables the minimum feature size of circuit components to be reduced. However, as the minimum feature size is reduced, the edge roughness of the photoresist layer typically becomes more difficult to control.
Therefore, there is a need for improved techniques for controlling line edge/width roughness.